MB w212 v6. Misfiring cylinder 1; OK after restart

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  • #12344
    Dutch
    Participant

      My MB E350 cgi (w212 2009 190.000 km) misfires in the mornings and then runs on 5 cylinders. When I restart (even after 10 seconds or so) the problem is gone. If I don’t restart the problem sticks. Two or three minutes after every start the car holds back a little for a minute. I use an iCarsoft MBll scanner and get code P0301. The car is professionally maintained. The ignition spark of cylinder one is 1857 cnt. That of the other cylinders 0 or 1 cnt. Sparkplug OK. Injector OK. Ignition coil OK. Wiring OK. Compression OK. Fuel pressure OK. No intake airleak. (LTFT b1 1,6%, b2 6,3%; STFT b1 0,0%, b2 -3,9%). Anybody got a clue?

      #21707
      Alex Longpre
      Participant

        Does this happen every time you start the car or only if the car has been sitting for a while?

        #21782
        Importech
        Participant

          Hi, It sounds like maybe the #1 cylinder fuel injector is leaking fuel when the engine is off, fouling the spark plug.

          #21795
          Dutch
          Participant

            Hello Alex, thank you for responding. Only after the car has been sitting for a while. Usually for some ten hours or so.

            #21796
            Dutch
            Participant

              Hello Importech, thank you for responding. So far no one has come up with this suggestion. It does not seem to account for the holding back every run after the engine has heated up, though. Or do you think the problems are unrelated?

              #22016
              Alex Longpre
              Participant

                I was asking this because I’m a Mercedes dealership technician and one thing that I see happen now and then, is that when the car has been sitting for a while, the ME seems to lose trace of some of its injectors for a reason nobody seem to understand and then cuts power to that injector. The car then runs like cap and CEL stays ON until the car is restarted, then the problem goes away.

                But 10 hours is too short of a downtime for this to happen.

                The leaky injector scenario described above is not out of the question, we see that from time to time.

                #27589
                Dutch
                Participant

                  Solution found. Sparkplug cylinder one did not reach combustion chamber due to contamination of thread which made torque wrench click prematurely.Thread cleaned. Sparkplug in right position. Engine runs like clockwork.

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